1. Field of the invention
The present invention relates to a coating agent for paper and, more specifically, to a paper coating agent having excellent applicability through blade coaters or roll coaters.
2. Description of the prior art
Polyvinyl alcohol (hereinafter referred to as "PVA") has been widely used as a clear coating agent to improve the surface characteristics of paper, such as smoothness, luster and barrier properties, and as a binder for pigment coating. PVA is known to have excellent film formability and strength and is unrivaled by any other sizing agent with respect to these points.
However, as in recent years the application speed has been increasing or novel application process has appeared such as with roll coater, there have occurred several problems associated with conventional aqueous PVA solutions, which obstruct stable and uniform application. The problems are viscosity increase (dilatancy) under high shear rate conditions with blade coater, or formation of streaks or generation of mist-like scattering upon high-speed roll application.
Accordingly, an object of the present invention is to provide a PVA-based paper coating agent that has excellent applicability, while maintaining the above features of PVA, i.e. good film formability and strength.